I have done this before, and it works, but the client downloads every single file locally in the background before it's able to do the comparison. I suspect this is because WinDirStat requests metadata about the file itself, and the sync client needs to download the files in order to serve that metadata and/or file contents information to the application.
About a decade ago when I worked in IT I used Treesize Pro to scan SMB volumes and delete the MOVIES that employees had downloaded on their computers, which meant they were downloading MOVIES to our SAN because we used roaming profiles. I'll never get over that these people downloaded literal pirated movies to our servers. It was constant. I ended up putting file size limits on their directories, or a file extension block, I forget.
The free version can't scan network drives if the servers on a domain IIRC.
edit: Oh I thought I read SMB drive not google drive for some reason. I'm not sure if this does that or not. It's my favorite GUI so worth checking out.
Does anyone know anything close to WinDirStat for google drive? I really need something like this.